Synthesis of [carbonyl‐14C]‐labelled remoxipride and raclopride. Two potential neuroleptic agents

Abstract

AbstractThe synthesis of two benzamide derivatives labelled with carbon‐14 at the carboxamide position is described. The radioactive label was introduced by the reaction of 1,3‐dimethoxy‐2‐lithiobenzene with [14C]carbon dioxide to furnish 2,6‐dimethoxy[carboxy‐14C]benzoic acid (2). Halogenation of 2 with dioxane dibromide or sulphuryl chloride followed by reaction with thionyl chloride led to the corresponding labelled acid chlorides. These were reacted with (S)‐2‐(aminomethyl)‐1‐ethylpyrrolidine (5) and converted into [14C]remoxipride (6) and [14C]raclopride (8), respectively.